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Current IssueEditorial BoardOnline First ArticlesArchive

Full Research Article

Development of a Functional Dairy Product: Aloe vera and Kithul (Caryota urens) Treacle-enriched Cow Milk Curd

K
Kalaivizhi Varathanathan1,*
0009-0006-7477-4334
S
Susantha Piratheepan1
W
Weerasingha Diwakarage Isuru Prabhath Jayaweera1
T
Thasanthan Loganathan2
1Department of Animal Science, Faculty of Agriculture, University of Jaffna, Sri Lanka.
2Department of Radiography/Radiotherapy, Faculty of Allied Health Sciences, University of Peradeniya, Sri Lanka.

ABSTRACT

Background: This study aimed to develop a functional curd by incorporating aloe vera juice and kithul (Caryota urens) treacle into cow milk and to evaluate its physicochemical, sensory and microbial properties.

Methods: Aloe vera juice was first optimized with kithul treacle at concentrations of 8%, 16% and 24%, with 24% treacle identified as optimal based on sensory evaluation. This optimized aloe vera juice was then added to cow milk curd at varying levels (5%, 10%, 15%, 20% and 25%), alongside a control. Sensory evaluation was conducted using a nine-point hedonic scale with 60 semi-trained panelists. Physicochemical parameters, texture, pH, acidity and microbial safety were assessed across treatments.

Result: The 15% aloe vera juice curd (T4) achieved the highest overall sensory preference. Physicochemical analysis revealed increased protein, ash, carbohydrate and fiber contents in aloe vera curds compared to control, while fat content remained consistent. T4 exhibited optimal texture, viscosity and hardness. Aloe vera incorporation led to decreased pH and increased acidity. Microbial analysis confirmed the absence of E. coli and coliforms, with higher aloe vera levels contributing to reduced microbial growth and extended shelf life.

INTRODUCTION

Curd, a fermented dairy product, is highly valued for its nutritional benefits, enhanced digestibility and probiotic content, which support gut health and immunity (Hui et al., 2019; Boudreau and Beland, 2006; Kavanagh et al., 2019). Cow milk, rich in high-quality proteins, essential amino acids and micronutrients like calcium and riboflavin, is a cornerstone of dairy nutrition, promoting bone health and metabolic functions (Shetty and Shetty, 2018; Huth and DiRienzo, 2006). Aloe vera (Aloe barbadensis miller), known for its anti-inflammatory, antioxidant and antimicrobial properties, offers additional digestive and immune benefits (Radha et al., 2012; Salehi et al., 2018; Minjares-Fuentes and Femenia, 2019; Talukdar et al., 2023). Kithul treacle, derived from Caryota urens L., complements aloe vera with its antioxidant-rich composition and natural sweetness (Ratnasiri and Seneviratne, 2012). This study aimed to develop a functional curd by incorporating aloe vera juice, optimized with kithul treacle at 24%, into cow milk curd at varying levels (5–25%) alongside a control. These findings underscore the potential of integrating aloe vera juice and kithul treacle into curd production to create a nutritionally enriched, functional dairy product that appeals to health-conscious consumers while preserving traditional flavors.

MATERIALS AND METHODS

Study location and raw material collection
 
This study took place at the Department of Animal Science, Faculty of Agriculture, University of Jaffna, in partnership with a JICA-supported laboratory and infrastructure from March to August 2023. Cow milk was sourced from the Ariviyal Nagar farm. Curd culture came from the VRI, Peradeniya and kithul treacle from Kalawana. Laboratory equipment included autoclave, Soxhlet, Kjeldahl, muffle furnace, texture analyzer, colorimeter, pH meter, incubator, freezer and laminar-flow hood.
 
Preparation of mother culture and working culture
 
Powdered starter culture was stored at 4°C. To prepare the mother culture, 25 g of Anchor non-fat skim milk powder was mixed with 250/ ml of boiling water. Once fully dissolved and cooled to 45°C, the starter culture was added. The mixture was poured into 20 ml bottles and incubated at 30°C for 12-16 hours until thickened, then stored frozen until use. The working culture was prepared a day before production. One liter of cow milk was boiled and cooled to 30°C to eliminate unwanted microbes (De, 1986; Tamime and Robinson, 2007). After thawing, 20 ml of mother culture was added and the milk was incubated at 30°C for 12 hours (Bhat and Naik, 2013; Johns, 1960).
 
Preparation of aloe vera juice
 
Mature aloe vera leaves (≥3 years) were harvested for optimal gel and juice yield (Uppar et al., 2024). After thorough washing, thorns and leaf ends were removed and the leaves were filleted to extract the inner gel. The gel was blended with filtered water (0.5:1 ratio) to form aloe vera gel (Thu et al., 2023), then filtered through muslin cloth. The juice was heated at 70-80°C for 10-15 minutes to inactivate spoilage enzymes (Añibarro-Ortega et al., 2019; Hingne and Shelke, 2020). Kithul treacle was added at 8%, 16% and 24%, with optional preservatives (0.1% citric acid and 0.1% sodium benzoate) (Uppar et al., 2024). The final product was stored in airtight containers at 4°C in a cool, dry place to retain quality.
 
Sensory evaluation
 
Sensory acceptability was assessed by 40 semi-trained panelists using a 9-point hedonic scale (Ali et al., 2021; Freitas et al., 2021; Govindammal and Thangaraj, 2017; Inyang, 2018). Samples (30 mL) with 8%, 16% and 24% kithul treacle were coded and presented under controlled lighting, with palate cleansing between tastings (Magalhães and Cazal, 2021; Tt et al., 2020).
 
Sterilization of earthen pots
 
Package the final product, earthen pots were utilized. Before filling the samples into the pots, a thorough cleaning process was conducted using heated water. Subsequently, the pots were wholly sterilized by being placed in an oven at a temperature of 100°C for 6-7 hours (Gonzalez, 2007).
 
Preparation of curd with different levels of aloe vera juice sample
 
All equipment was sterilized (Ban et al., 2023). Milk was heated to 85°C, reduced, cooled, homogenized and inoculated with culture (Tadjine et al., 2021; Al-Taif et al., 2022; Tank et al., 2022). Aloe vera juice (5-25%) was added before incubation at 37°C for 16 hours.
 
Sensory evaluation 02
 
Sensory evaluation of aloe vera curd and control samples was conducted with 60 semi trained Agriculture students using a nine point hedonic scale under randomized, controlled conditions. Participants assessed appearance, aroma, texture, flavor and overall acceptability in 15-20 min sessions.
 
Proximate and microbial analysis
 
Moisture, fat, protein, total solids, pH and carbohydrates were analyzed. Moisture was measured by oven drying (AOAC 925.23, 2005). Protein was determined via Kjeldahl (AOAC 991.20, 2005). Fat was extracted using Soxhlet (AOAC 989.05, 2000). Fiber was analyzed with ANKOM 200 (AOAC 985.29, 2000). Ash was incinerated at 550°C (AOAC 923.03, 2005). Carbohydrates were calculated by difference (IAL, 2005). Energy was measured by bomb calorimeter (AOAC 935.29, 2000). Microbiological tests ensured hygienic quality (APHA, 2001; Brasil, 2001).
 
Analysis of physiochemical parameters and shelf-life evaluation
 
pH was measured using a pH meter. Titratable acidity was determined by acid-base titration (AOAC 947.05, 2019) and CIE color coordinates (Akalın et al., 2008). Texture was analyzed with an IMADA texture analyzer (model FRTS). Shelf-life was evaluated via microbial analysis, pH and titratable acidity, measured on production day and day 14. Sensory panelists assessed visual acceptability, mouth feel (juiciness), color, aroma, flavor/taste and overall impression.
 
Evaluation of cost of production
 
Production cost was assessed for each of the six treatments individually by using the following components; Cow milk, aloe vera juice, starter culture, earthen pot and Unit price (80 ml pot).
 
Experimental design and statistical analysis
 
Physicochemical data were analyzed using the General Linear Model in SAS software, following a completely randomized design. Mean scores for storage periods and formulations were compared via Duncan’s Multiple Range Test at p≤0.05. Statistical analyses used SAS version 6.0.10. Sensory acceptance data, based on a 9-point hedonic scale, were analyzed using SPSS version 20.

RESULTS AND DISCUSSION

Proximate analysis of aloe vera juice
 
Results for the proximate composition of each parameter of aloe vera juice are represented Table 1.

Table 1: Proximate composition of aloe vera juice, including moisture, protein, carbohydrate, fat, fiber and ash content.


       
Proximate analysis of aloe vera juice revealed 55.97% moisture, lower than typical 98% in aloe gel (Raza et al., 2024), enhancing stability. Protein (0.322%) supported cellular functions (Zhang et al., 2018), while low fat (2.096%) suited health-oriented beverages. Carbohydrates (19.69%) provided energy and fiber (0.989%) aided gut health (Khan et al., 2015). Ash (0.728%) indicated mineral content. Bioactive compounds offered antioxidant and anti-inflammatory benefits (Tariq et al., 2023; Patel and Gupta, 2019; Mamdouh and Youssef, 2022). High moisture requires preservation to extend shelf life (Khan et al., 2015).
 
Physicochemical properties of aloe vera juice (Table 2)
 
Aloe vera juice exhibited a pH of 6.0±0.2, slightly acidic, enhancing stability and taste, consistent with (Soltanizadeh and Mousavinejad, 2015); (pH 4.98±0.64). Its smooth, slightly dense texture and 17.25% Brix indicate balanced viscosity for consumer appeal. Kithul treacle can enhance sweetness and texture (Monteiro-Alfredo et al., 2021; Sharma et al., 2015). Energy content was 125 kJ±0.2 kJ, higher than Singh’s (2022; 62.76 ±0.65 kJ), due to carbohydrate and fat variations. Excessive consumption may cause gastrointestinal discomfort (Banjare et al., 2014).

Table 2: Physicochemical properties of Aloe vera juice was used in Aloe vera curd preparation.


 
Sensory attributes
 
Optimization of kithul treacle level in aloe vera juice
 
Kithul treacle (Table 3) enhanced sensory attributes of aloe vera juice, improving overall acceptability (6.38 to 8.47) and appearance due to its color and gloss (Forde, 2024; Aheeshan et al., 2022). Aroma, flavor and consistency peaked at T3, highlighting the importance of sweetness balance (Ray, 2021; Bechoff et al., 2023) (Fig 1 and 2).

Table 3: Result of sensory attributes of optimization of kithul treacle in Aloe vera juice.



Fig 1: Radar graph for sensory evaluation of different levels of kithul treacle in Aloe vera juice samples.



Fig 2: Mean plot for overall acceptability in the sensory attribute of different levels of Kithul treacle in Aloe vera juice samples.


 
Curd with different aloe vera juice levels
 
Sensory evaluation of curd with different level of aloe vera juice level samples were carried out to confirm the product acceptability by the consumers. Chemical characteristics were the most important indicators of quality measures of formulated aloe vera curd. Mean values observed for the physiochemical parameters in aloe vera curd samples were shown in Table 4.

Table 4: Result of sensory attributes of different levels of aloe vera juice level in curd.


       
Aloe vera juice significantly improved curd’s sensory attributes (p<0.001), with T4 showing highest scores in overall acceptability, appearance, aroma, flavor and texture. ANOVA confirmed strong effects despite heteroscedasticity, highlighting aloe vera’s potential in enhancing dairy product quality and consumer appeal (Fig 3 and 4).

Fig 3: Radar graph for sensory evaluation of different levels of Aloe vera juice level in curd.



Fig 4: Mean plot for overall acceptability in the sensory attribute of different levels of Aloe vera juice level in curd.


 
Proximate analysis of aloe vera curd
 
Average proximate analysis values in aloe vera curd samples (Table 5).

Table 5: The average pH values recorded among various Aloe vera curd formulations.


 
Moisture content (Fig 5)
 
Data from Table 5 and Fig 5 showed a clear relationship between aloe vera juice concentration and moisture content in curd formulations. Significant differences (p<0.05) were observed, with T1 having the highest moisture content (82.992±0.004) and T6 the lowest (74.301±0.005). Higher moisture contributed to a softer, more palatable texture (Pojić et al., 2015), while lower moisture created firmer textures appealing to some consumers (Nielsen, 2017). The decrease in moisture as aloe vera concentration increased highlighted aloe vera’s gel-like, low-water composition influencing water retention, aligning with Sonawane (2020). Striking an optimal balance is critical, as excessively low moisture may reduce palatability and consumer acceptance (Nurzantry and Widayanti, 2015).

Fig 5: Changes in average moisture percentage of different treatments.


 
Ash content
 
Changes in average ash percentage among different treatments of curd.
       
The study showed significant differences (p<0.05) in ash content among aloe vera curd formulations, ranging from 0.6505±0.004 (T1) to 3.701±0.004 (T4). T4’s higher ash content reflects greater mineral enrichment, boosting nutritional value with calcium, phosphorus, potassium and magnesium (Ikram et al., 2020). Variability likely arises from ingredient levels or processing conditions affecting mineral retention (Ismail, 2017). While T4’s mineral-rich profile suits health-conscious consumers, balancing functionality with flavor and texture is key for wider acceptance (Karmali et al., 2023).
 
Fat content
 
Aloe vera juice incorporation significantly reduced curd fat content, decreasing from 4.5±0.14 (T1) to 3.218 ±0.006 (T6) as aloe concentration increased (Fig 6), meeting Sri Lankan Standards (SLS 223: 2016). Aloe’s polysaccharides, polyphenols and sterols lower lipid levels, with lipases aiding fat breakdown (Forsyth, 2023; Surjushe et al., 2008; Rajasekaran, 2005). Antioxidants prevent lipid peroxidation (Grace et al., 2014). Lower fat appeals to health-conscious consumers but may affect flavor and texture, necessitating balance (Fontecha and Juárez, 2017).

Fig 6: Average fat percentage of aloe vera curd across different treatments.


 
Protein content
 
Results of this study indicated a significant enhancement in protein content in curd samples with the addition of aloe vera juice. The observed range (Table 5) for protein content extended from 4.501±0.004 in Treatment T1 to 22.902±0.004 in Treatment T4, indicated a clear positive correlation between increased aloe vera concentration and crude protein content up to a certain threshold. This finding aligned with the hypothesis that aloe vera juice contributes bioactive compounds that may facilitate protein synthesis or preservation (Surjushe, 2008) (Fig 7).

Fig 7: Changes in average crude protein percentage across different treatments of Aloe vera curd.


       
Protein content rose from T1 (4.501±0.004) to T4 (22.902±0.007), then declined, suggesting optimal aloe levels enhance synthesis via amino acids and vitamins (Tarhan and Kaya, 2021). Fermentation aids peptide bioavailability (Parlapanova, 1990), while improved calcium absorption enhances nutrition (Kiełczewska et al., 2022). Balanced inclusion is essential.
 
Fiber content
 
The incorporation of aloe vera juice significantly improved the nutritional profile of curd, particularly by increasing its dietary fiber and protein content. These findings aligned with previous studies on aloe vera’s impact on nutritional fortification (Banakar et al., 2021) (Fig 8).

Fig 8: Changes in average fiber percentage of different curd treatments.


       
Fiber content significantly increased from T2 to T6 due to aloe vera’s soluble and insoluble fibers, while T1 (milk alone) had none (Hajirostamloo, 2009). Protein also rose, reaching 2.903±0.014 in T6, supported by aloe vera’s amino acids and nutrients. The curd offers fiber, protein, antioxidants and prebiotic benefits (Bankar et al., 2022) (Fig 9).

Fig 9: Changes in average carbohydrate percentage among treatments of aloe vera curd.


 
Carbohydrate content
 
Aloe vera juice significantly increased curd carbohydrate content from 4.678±0.005 (T1) to 8.433±0.005 (T6) (p<0.05), due to its natural sugars and polysaccharides (Babatunde et al., 2022; Surjushe, 2008). These enhance energy, digestion and prebiotic effects (Slavin, 2013; Ghalandari et al., 2017).
 
Analysis of physicochemical properties of aloe vera curd
Estimation of pH in aloe vera curd formulations
 
According to Sri Lankan Standards (SLS 731, 2008), optimum curd pH is 4.5±0.024. Aloe vera curd pH significantly differed (p<0.05) from Day 1 (4.051-4.724) to Day 15 (4.013-4.605), with increased aloe lowering pH via organic acids (Selamoglu, 2018). Beyond T4, pH rose due to dilution and buffering (Alhamid and Al Mousawi, 2022). Lactic fermentation further reduced pH (Mozzi, 2016). Storage over 15 days at 4°C increased acidity, reducing palatability (Usha and Appaiah, 2012) (Fig 10, 11 and Table 5) .

Fig 10: Average pH values in curd sample first day of production.



Fig 11: Average pH values 14 days after the production in curd samples.


 
Determination of titratable acidity
 
According to the Sri Lankan Standards (SLS 731, 2008), the optimum acidity value for curd ranges from 0.8 to 1.25% (Fig 12 and Fig 13) Significant differences (p<0.05) in titratable acidity were observed among aloe vera curd samples on Day 1 and Day 15. Acidity ranged from 0.619±0.001 (T1) to 0.920±0.003 (T4) on Day 1, increasing to 0.756±0.002 (T1) and 1.146±0.006 (T4) by Day 15. The increase from T1 to T4 was due to higher aloe vera juice concentrations containing organic acids like citric and malic acids (Selamoglu, 2018). A decline from T4 to T6 likely resulted from dilution effects and aloe vera’s buffering capacity (Alhamid and Al Mousawi, 2022). Interactions with kithul treacle and lactic acid fermentation during storage also influenced acidity (Weeraratne and Ekanayake, 2022; Mozzi, 2016). These results emphasize aloe vera’s role in modulating curd acidity.

Fig 12: Average titratable acidity won first day of production in curd samples.



Fig 13: Average titratable acidity in 14 days after the production in curd samples.


 
Determination of texture (Table 6)
 
The data showed significant differences (p<0.05p) in hardness and viscosity among treatments. Hardness values ranged from 0.753±0.005 (T1) to 1.613±0.005 (T4), while viscosity ranged from 15227.000±53.435 (T1) to 59683.500±17.078 (T4).

Table 6: Average hardness and viscosity values in Aloe vera curd samples.


       
Hardness and viscosity increased from T1 to T4 as aloe vera polysaccharides enhanced protein cross-linking and water retention (Eshun and He, 2004; Cervantes-Martínez et al., 2014). Acemannan thickened the curd (Kavitake, 2019). Declines beyond T4 resulted from aloe enzymes breaking down structure and dilution reducing viscosity (Jain, 2016; Bai et al., 2023).

Determination of color
 
Significant differences (p<0.05) were observed in color parameters among aloe vera curd treatments. As aloe vera juice concentration increased from T1 to T6, the L* value decreased, indicating a darker appearance, while a* and b* values declined, reflecting reduced red and yellow tones. This darkening was attributed to kithul treacle, a dark brown sweetener, whose sugars and caramelized compounds induced browning via Maillard reactions chemical interactions between amino acids and reducing sugars during processing (Wijesinghe, 2018; Elleuch, 2011; Deepa, 2016). These findings highlight the combined impact of aloe vera juice and kithul treacle on curd color, shaped by ingredient interactions and browning reactions.
 
Microbiological analysis
 
Determination of average yeast count
 
No yeast detected on Days/ 1 and 5 in any treatment. All treatments met SLS/ 731:2008 limits (<1,000 CFU/g) until Day 15. From Day 16 onward, T1-T6 sequentially exceeded the limit, culminating in all treatments violating it by Days/ 19-20. Higher aloe vera concentrations delayed yeast growth via antifungal compounds.
 
Determinations of total mold count
 
No mold was detected in any treatment on days 1, 5 and 10. According to SLS 731 (2008), curd should contain fewer than 10 molds per gram. On day 15, molds were absent in T2–T6, while T1 recorded 7.5±1.29, within the acceptable limit. On day 16, T4-T6 remained mold-free; T2 (6.75±0.50) and T3 (5.5±0.58) were within limits, whereas T1 (867.75±8.06) exceeded the standard. By day 17, T2 (952.25±6.60) and T3 (740.25 ±10.81) surpassed limits, while T4 (8±0.82), T5 (7.25±0.96) and T6 remained safe.

On days 19 and 20, all treatments exceeded SLS limits. Yeast counts decreased with increasing aloe vera concentration, indicating antimicrobial effects of aloe bioactive compounds (Srikanth, 2017).
 
Determination of total plate count
 
The permissible total plate count (TPC) for curd is <10w  (Chaudhary et al., 2011). None of the treatments exceeded this limit during the initial storage stages (Days 1, 5, 10, 15). On Day 16, T1 (1.41×10x ±0.009×10x ) exceeded the limit, while others remained compliant. By Day 17, T2 (2.21×10x ±0.020×10x ) and T3 (1.62×10x  ±0.035×10x ) also surpassed the limit, with T4, T5 and T6 still within acceptable levels. On Day 18, T4 and T5 exceeded the limit, leaving T6 as the only compliant treatment. Beyond Day 18, all treatments surpassed the permissible limit, with T6 showing the longest storage stability (18 days) compared to T1 (15 days). Results demonstrate that higher aloe vera juice concentrations (T6) extended curd shelf life due to aloe vera’s bioactive compounds and antimicrobial properties (Srikanth, 2017; Alam et al., 2022). These findings underline aloe vera’s potential to enhance curd stability and storage duration, benefiting the dairy industry.
 
Determination of E. coli and coliform count
 
All aloe vera curd treatments complied with SLS 824:1989, showing no E. coli or coliforms throughout storage, indicating hygienic preparation and aloe vera’s antimicrobial action. Bioactive compounds like acemannan and aloin contributed to microbial safety and extended shelf life (Hamman, 2008; Kambizi and Afolayan, 2001).
 
Cost-benefit analysis
 
Table 7 shown the cost of production of various formulated aloe vera curd samples produced from 6L of cow milk. The cost of producing by using 1L of cow milk and 1L of aloe vera juice was LKR 620.00, T2 was LKR628.50, T3 was LKR 637.00, T4 was LKR 645.50, T5 was LKR 654.00 and T6 was 662.50. Aloe vera curd samples could be quickly released to the food market since this sample has higher nutritional value and acceptable cost compared to the regular market price. Commercially available honey-added NLDB curd was Rs150.00 (Sharma, 2010).

Table 7: Cost benefit analysis.

CONCLUSION

This study demonstrated that curd produced by blending cow milk and aloe vera juice, sweetened with kithul treacle, offers a convenient, ready-to-eat product with enhanced physical, chemical and sensory attributes. Kithul treacle, a natural sweetener rich in antioxidants, minerals and proteins, replaced white sugar, while aloe vera juice contributed vitamins, minerals, enzymes, polysaccharides and antioxidants, enhancing nutritional and health benefits. Optimal quality was achieved in T4, which exhibited superior nutritional value, acceptability, a light brown color, firm consistency, smooth texture and pleasant aroma. The production cost of T4 (80 ml) was Rs. 117.00, with potential cost reductions through alternative packaging. T4 also offered an extended shelf life of 18 days, outperforming commercially available honey-added NLDB curd in cost and quality. This innovative product promises to revolutionize the dairy industry by providing an affordable, nutrient-rich curd option that aligns with consumer preferences and market demands.

CONFLICT OF INTEREST

The authors declare that there is no conflict of interest regarding the publication of this manuscript.

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    Full Research Article

    Development of a Functional Dairy Product: Aloe vera and Kithul (Caryota urens) Treacle-enriched Cow Milk Curd

    K
    Kalaivizhi Varathanathan1,*
    0009-0006-7477-4334
    S
    Susantha Piratheepan1
    W
    Weerasingha Diwakarage Isuru Prabhath Jayaweera1
    T
    Thasanthan Loganathan2
    1Department of Animal Science, Faculty of Agriculture, University of Jaffna, Sri Lanka.
    2Department of Radiography/Radiotherapy, Faculty of Allied Health Sciences, University of Peradeniya, Sri Lanka.

    ABSTRACT

    Background: This study aimed to develop a functional curd by incorporating aloe vera juice and kithul (Caryota urens) treacle into cow milk and to evaluate its physicochemical, sensory and microbial properties.

    Methods: Aloe vera juice was first optimized with kithul treacle at concentrations of 8%, 16% and 24%, with 24% treacle identified as optimal based on sensory evaluation. This optimized aloe vera juice was then added to cow milk curd at varying levels (5%, 10%, 15%, 20% and 25%), alongside a control. Sensory evaluation was conducted using a nine-point hedonic scale with 60 semi-trained panelists. Physicochemical parameters, texture, pH, acidity and microbial safety were assessed across treatments.

    Result: The 15% aloe vera juice curd (T4) achieved the highest overall sensory preference. Physicochemical analysis revealed increased protein, ash, carbohydrate and fiber contents in aloe vera curds compared to control, while fat content remained consistent. T4 exhibited optimal texture, viscosity and hardness. Aloe vera incorporation led to decreased pH and increased acidity. Microbial analysis confirmed the absence of E. coli and coliforms, with higher aloe vera levels contributing to reduced microbial growth and extended shelf life.

    INTRODUCTION

    Curd, a fermented dairy product, is highly valued for its nutritional benefits, enhanced digestibility and probiotic content, which support gut health and immunity (Hui et al., 2019; Boudreau and Beland, 2006; Kavanagh et al., 2019). Cow milk, rich in high-quality proteins, essential amino acids and micronutrients like calcium and riboflavin, is a cornerstone of dairy nutrition, promoting bone health and metabolic functions (Shetty and Shetty, 2018; Huth and DiRienzo, 2006). Aloe vera (Aloe barbadensis miller), known for its anti-inflammatory, antioxidant and antimicrobial properties, offers additional digestive and immune benefits (Radha et al., 2012; Salehi et al., 2018; Minjares-Fuentes and Femenia, 2019; Talukdar et al., 2023). Kithul treacle, derived from Caryota urens L., complements aloe vera with its antioxidant-rich composition and natural sweetness (Ratnasiri and Seneviratne, 2012). This study aimed to develop a functional curd by incorporating aloe vera juice, optimized with kithul treacle at 24%, into cow milk curd at varying levels (5–25%) alongside a control. These findings underscore the potential of integrating aloe vera juice and kithul treacle into curd production to create a nutritionally enriched, functional dairy product that appeals to health-conscious consumers while preserving traditional flavors.

    MATERIALS AND METHODS

    Study location and raw material collection
     
    This study took place at the Department of Animal Science, Faculty of Agriculture, University of Jaffna, in partnership with a JICA-supported laboratory and infrastructure from March to August 2023. Cow milk was sourced from the Ariviyal Nagar farm. Curd culture came from the VRI, Peradeniya and kithul treacle from Kalawana. Laboratory equipment included autoclave, Soxhlet, Kjeldahl, muffle furnace, texture analyzer, colorimeter, pH meter, incubator, freezer and laminar-flow hood.
     
    Preparation of mother culture and working culture
     
    Powdered starter culture was stored at 4°C. To prepare the mother culture, 25 g of Anchor non-fat skim milk powder was mixed with 250/ ml of boiling water. Once fully dissolved and cooled to 45°C, the starter culture was added. The mixture was poured into 20 ml bottles and incubated at 30°C for 12-16 hours until thickened, then stored frozen until use. The working culture was prepared a day before production. One liter of cow milk was boiled and cooled to 30°C to eliminate unwanted microbes (De, 1986; Tamime and Robinson, 2007). After thawing, 20 ml of mother culture was added and the milk was incubated at 30°C for 12 hours (Bhat and Naik, 2013; Johns, 1960).
     
    Preparation of aloe vera juice
     
    Mature aloe vera leaves (≥3 years) were harvested for optimal gel and juice yield (Uppar et al., 2024). After thorough washing, thorns and leaf ends were removed and the leaves were filleted to extract the inner gel. The gel was blended with filtered water (0.5:1 ratio) to form aloe vera gel (Thu et al., 2023), then filtered through muslin cloth. The juice was heated at 70-80°C for 10-15 minutes to inactivate spoilage enzymes (Añibarro-Ortega et al., 2019; Hingne and Shelke, 2020). Kithul treacle was added at 8%, 16% and 24%, with optional preservatives (0.1% citric acid and 0.1% sodium benzoate) (Uppar et al., 2024). The final product was stored in airtight containers at 4°C in a cool, dry place to retain quality.
     
    Sensory evaluation
     
    Sensory acceptability was assessed by 40 semi-trained panelists using a 9-point hedonic scale (Ali et al., 2021; Freitas et al., 2021; Govindammal and Thangaraj, 2017; Inyang, 2018). Samples (30 mL) with 8%, 16% and 24% kithul treacle were coded and presented under controlled lighting, with palate cleansing between tastings (Magalhães and Cazal, 2021; Tt et al., 2020).
     
    Sterilization of earthen pots
     
    Package the final product, earthen pots were utilized. Before filling the samples into the pots, a thorough cleaning process was conducted using heated water. Subsequently, the pots were wholly sterilized by being placed in an oven at a temperature of 100°C for 6-7 hours (Gonzalez, 2007).
     
    Preparation of curd with different levels of aloe vera juice sample
     
    All equipment was sterilized (Ban et al., 2023). Milk was heated to 85°C, reduced, cooled, homogenized and inoculated with culture (Tadjine et al., 2021; Al-Taif et al., 2022; Tank et al., 2022). Aloe vera juice (5-25%) was added before incubation at 37°C for 16 hours.
     
    Sensory evaluation 02
     
    Sensory evaluation of aloe vera curd and control samples was conducted with 60 semi trained Agriculture students using a nine point hedonic scale under randomized, controlled conditions. Participants assessed appearance, aroma, texture, flavor and overall acceptability in 15-20 min sessions.
     
    Proximate and microbial analysis
     
    Moisture, fat, protein, total solids, pH and carbohydrates were analyzed. Moisture was measured by oven drying (AOAC 925.23, 2005). Protein was determined via Kjeldahl (AOAC 991.20, 2005). Fat was extracted using Soxhlet (AOAC 989.05, 2000). Fiber was analyzed with ANKOM 200 (AOAC 985.29, 2000). Ash was incinerated at 550°C (AOAC 923.03, 2005). Carbohydrates were calculated by difference (IAL, 2005). Energy was measured by bomb calorimeter (AOAC 935.29, 2000). Microbiological tests ensured hygienic quality (APHA, 2001; Brasil, 2001).
     
    Analysis of physiochemical parameters and shelf-life evaluation
     
    pH was measured using a pH meter. Titratable acidity was determined by acid-base titration (AOAC 947.05, 2019) and CIE color coordinates (Akalın et al., 2008). Texture was analyzed with an IMADA texture analyzer (model FRTS). Shelf-life was evaluated via microbial analysis, pH and titratable acidity, measured on production day and day 14. Sensory panelists assessed visual acceptability, mouth feel (juiciness), color, aroma, flavor/taste and overall impression.
     
    Evaluation of cost of production
     
    Production cost was assessed for each of the six treatments individually by using the following components; Cow milk, aloe vera juice, starter culture, earthen pot and Unit price (80 ml pot).
     
    Experimental design and statistical analysis
     
    Physicochemical data were analyzed using the General Linear Model in SAS software, following a completely randomized design. Mean scores for storage periods and formulations were compared via Duncan’s Multiple Range Test at p≤0.05. Statistical analyses used SAS version 6.0.10. Sensory acceptance data, based on a 9-point hedonic scale, were analyzed using SPSS version 20.

    RESULTS AND DISCUSSION

    Proximate analysis of aloe vera juice
     
    Results for the proximate composition of each parameter of aloe vera juice are represented Table 1.

    Table 1: Proximate composition of aloe vera juice, including moisture, protein, carbohydrate, fat, fiber and ash content.


           
    Proximate analysis of aloe vera juice revealed 55.97% moisture, lower than typical 98% in aloe gel (Raza et al., 2024), enhancing stability. Protein (0.322%) supported cellular functions (Zhang et al., 2018), while low fat (2.096%) suited health-oriented beverages. Carbohydrates (19.69%) provided energy and fiber (0.989%) aided gut health (Khan et al., 2015). Ash (0.728%) indicated mineral content. Bioactive compounds offered antioxidant and anti-inflammatory benefits (Tariq et al., 2023; Patel and Gupta, 2019; Mamdouh and Youssef, 2022). High moisture requires preservation to extend shelf life (Khan et al., 2015).
     
    Physicochemical properties of aloe vera juice (Table 2)
     
    Aloe vera juice exhibited a pH of 6.0±0.2, slightly acidic, enhancing stability and taste, consistent with (Soltanizadeh and Mousavinejad, 2015); (pH 4.98±0.64). Its smooth, slightly dense texture and 17.25% Brix indicate balanced viscosity for consumer appeal. Kithul treacle can enhance sweetness and texture (Monteiro-Alfredo et al., 2021; Sharma et al., 2015). Energy content was 125 kJ±0.2 kJ, higher than Singh’s (2022; 62.76 ±0.65 kJ), due to carbohydrate and fat variations. Excessive consumption may cause gastrointestinal discomfort (Banjare et al., 2014).

    Table 2: Physicochemical properties of Aloe vera juice was used in Aloe vera curd preparation.


     
    Sensory attributes
     
    Optimization of kithul treacle level in aloe vera juice
     
    Kithul treacle (Table 3) enhanced sensory attributes of aloe vera juice, improving overall acceptability (6.38 to 8.47) and appearance due to its color and gloss (Forde, 2024; Aheeshan et al., 2022). Aroma, flavor and consistency peaked at T3, highlighting the importance of sweetness balance (Ray, 2021; Bechoff et al., 2023) (Fig 1 and 2).

    Table 3: Result of sensory attributes of optimization of kithul treacle in Aloe vera juice.



    Fig 1: Radar graph for sensory evaluation of different levels of kithul treacle in Aloe vera juice samples.



    Fig 2: Mean plot for overall acceptability in the sensory attribute of different levels of Kithul treacle in Aloe vera juice samples.


     
    Curd with different aloe vera juice levels
     
    Sensory evaluation of curd with different level of aloe vera juice level samples were carried out to confirm the product acceptability by the consumers. Chemical characteristics were the most important indicators of quality measures of formulated aloe vera curd. Mean values observed for the physiochemical parameters in aloe vera curd samples were shown in Table 4.

    Table 4: Result of sensory attributes of different levels of aloe vera juice level in curd.


           
    Aloe vera juice significantly improved curd’s sensory attributes (p<0.001), with T4 showing highest scores in overall acceptability, appearance, aroma, flavor and texture. ANOVA confirmed strong effects despite heteroscedasticity, highlighting aloe vera’s potential in enhancing dairy product quality and consumer appeal (Fig 3 and 4).

    Fig 3: Radar graph for sensory evaluation of different levels of Aloe vera juice level in curd.



    Fig 4: Mean plot for overall acceptability in the sensory attribute of different levels of Aloe vera juice level in curd.


     
    Proximate analysis of aloe vera curd
     
    Average proximate analysis values in aloe vera curd samples (Table 5).

    Table 5: The average pH values recorded among various Aloe vera curd formulations.


     
    Moisture content (Fig 5)
     
    Data from Table 5 and Fig 5 showed a clear relationship between aloe vera juice concentration and moisture content in curd formulations. Significant differences (p<0.05) were observed, with T1 having the highest moisture content (82.992±0.004) and T6 the lowest (74.301±0.005). Higher moisture contributed to a softer, more palatable texture (Pojić et al., 2015), while lower moisture created firmer textures appealing to some consumers (Nielsen, 2017). The decrease in moisture as aloe vera concentration increased highlighted aloe vera’s gel-like, low-water composition influencing water retention, aligning with Sonawane (2020). Striking an optimal balance is critical, as excessively low moisture may reduce palatability and consumer acceptance (Nurzantry and Widayanti, 2015).

    Fig 5: Changes in average moisture percentage of different treatments.


     
    Ash content
     
    Changes in average ash percentage among different treatments of curd.
           
    The study showed significant differences (p<0.05) in ash content among aloe vera curd formulations, ranging from 0.6505±0.004 (T1) to 3.701±0.004 (T4). T4’s higher ash content reflects greater mineral enrichment, boosting nutritional value with calcium, phosphorus, potassium and magnesium (Ikram et al., 2020). Variability likely arises from ingredient levels or processing conditions affecting mineral retention (Ismail, 2017). While T4’s mineral-rich profile suits health-conscious consumers, balancing functionality with flavor and texture is key for wider acceptance (Karmali et al., 2023).
     
    Fat content
     
    Aloe vera juice incorporation significantly reduced curd fat content, decreasing from 4.5±0.14 (T1) to 3.218 ±0.006 (T6) as aloe concentration increased (Fig 6), meeting Sri Lankan Standards (SLS 223: 2016). Aloe’s polysaccharides, polyphenols and sterols lower lipid levels, with lipases aiding fat breakdown (Forsyth, 2023; Surjushe et al., 2008; Rajasekaran, 2005). Antioxidants prevent lipid peroxidation (Grace et al., 2014). Lower fat appeals to health-conscious consumers but may affect flavor and texture, necessitating balance (Fontecha and Juárez, 2017).

    Fig 6: Average fat percentage of aloe vera curd across different treatments.


     
    Protein content
     
    Results of this study indicated a significant enhancement in protein content in curd samples with the addition of aloe vera juice. The observed range (Table 5) for protein content extended from 4.501±0.004 in Treatment T1 to 22.902±0.004 in Treatment T4, indicated a clear positive correlation between increased aloe vera concentration and crude protein content up to a certain threshold. This finding aligned with the hypothesis that aloe vera juice contributes bioactive compounds that may facilitate protein synthesis or preservation (Surjushe, 2008) (Fig 7).

    Fig 7: Changes in average crude protein percentage across different treatments of Aloe vera curd.


           
    Protein content rose from T1 (4.501±0.004) to T4 (22.902±0.007), then declined, suggesting optimal aloe levels enhance synthesis via amino acids and vitamins (Tarhan and Kaya, 2021). Fermentation aids peptide bioavailability (Parlapanova, 1990), while improved calcium absorption enhances nutrition (Kiełczewska et al., 2022). Balanced inclusion is essential.
     
    Fiber content
     
    The incorporation of aloe vera juice significantly improved the nutritional profile of curd, particularly by increasing its dietary fiber and protein content. These findings aligned with previous studies on aloe vera’s impact on nutritional fortification (Banakar et al., 2021) (Fig 8).

    Fig 8: Changes in average fiber percentage of different curd treatments.


           
    Fiber content significantly increased from T2 to T6 due to aloe vera’s soluble and insoluble fibers, while T1 (milk alone) had none (Hajirostamloo, 2009). Protein also rose, reaching 2.903±0.014 in T6, supported by aloe vera’s amino acids and nutrients. The curd offers fiber, protein, antioxidants and prebiotic benefits (Bankar et al., 2022) (Fig 9).

    Fig 9: Changes in average carbohydrate percentage among treatments of aloe vera curd.


     
    Carbohydrate content
     
    Aloe vera juice significantly increased curd carbohydrate content from 4.678±0.005 (T1) to 8.433±0.005 (T6) (p<0.05), due to its natural sugars and polysaccharides (Babatunde et al., 2022; Surjushe, 2008). These enhance energy, digestion and prebiotic effects (Slavin, 2013; Ghalandari et al., 2017).
     
    Analysis of physicochemical properties of aloe vera curd
    Estimation of pH in aloe vera curd formulations
     
    According to Sri Lankan Standards (SLS 731, 2008), optimum curd pH is 4.5±0.024. Aloe vera curd pH significantly differed (p<0.05) from Day 1 (4.051-4.724) to Day 15 (4.013-4.605), with increased aloe lowering pH via organic acids (Selamoglu, 2018). Beyond T4, pH rose due to dilution and buffering (Alhamid and Al Mousawi, 2022). Lactic fermentation further reduced pH (Mozzi, 2016). Storage over 15 days at 4°C increased acidity, reducing palatability (Usha and Appaiah, 2012) (Fig 10, 11 and Table 5) .

    Fig 10: Average pH values in curd sample first day of production.



    Fig 11: Average pH values 14 days after the production in curd samples.


     
    Determination of titratable acidity
     
    According to the Sri Lankan Standards (SLS 731, 2008), the optimum acidity value for curd ranges from 0.8 to 1.25% (Fig 12 and Fig 13) Significant differences (p<0.05) in titratable acidity were observed among aloe vera curd samples on Day 1 and Day 15. Acidity ranged from 0.619±0.001 (T1) to 0.920±0.003 (T4) on Day 1, increasing to 0.756±0.002 (T1) and 1.146±0.006 (T4) by Day 15. The increase from T1 to T4 was due to higher aloe vera juice concentrations containing organic acids like citric and malic acids (Selamoglu, 2018). A decline from T4 to T6 likely resulted from dilution effects and aloe vera’s buffering capacity (Alhamid and Al Mousawi, 2022). Interactions with kithul treacle and lactic acid fermentation during storage also influenced acidity (Weeraratne and Ekanayake, 2022; Mozzi, 2016). These results emphasize aloe vera’s role in modulating curd acidity.

    Fig 12: Average titratable acidity won first day of production in curd samples.



    Fig 13: Average titratable acidity in 14 days after the production in curd samples.


     
    Determination of texture (Table 6)
     
    The data showed significant differences (p<0.05p) in hardness and viscosity among treatments. Hardness values ranged from 0.753±0.005 (T1) to 1.613±0.005 (T4), while viscosity ranged from 15227.000±53.435 (T1) to 59683.500±17.078 (T4).

    Table 6: Average hardness and viscosity values in Aloe vera curd samples.


           
    Hardness and viscosity increased from T1 to T4 as aloe vera polysaccharides enhanced protein cross-linking and water retention (Eshun and He, 2004; Cervantes-Martínez et al., 2014). Acemannan thickened the curd (Kavitake, 2019). Declines beyond T4 resulted from aloe enzymes breaking down structure and dilution reducing viscosity (Jain, 2016; Bai et al., 2023).

    Determination of color
     
    Significant differences (p<0.05) were observed in color parameters among aloe vera curd treatments. As aloe vera juice concentration increased from T1 to T6, the L* value decreased, indicating a darker appearance, while a* and b* values declined, reflecting reduced red and yellow tones. This darkening was attributed to kithul treacle, a dark brown sweetener, whose sugars and caramelized compounds induced browning via Maillard reactions chemical interactions between amino acids and reducing sugars during processing (Wijesinghe, 2018; Elleuch, 2011; Deepa, 2016). These findings highlight the combined impact of aloe vera juice and kithul treacle on curd color, shaped by ingredient interactions and browning reactions.
     
    Microbiological analysis
     
    Determination of average yeast count
     
    No yeast detected on Days/ 1 and 5 in any treatment. All treatments met SLS/ 731:2008 limits (<1,000 CFU/g) until Day 15. From Day 16 onward, T1-T6 sequentially exceeded the limit, culminating in all treatments violating it by Days/ 19-20. Higher aloe vera concentrations delayed yeast growth via antifungal compounds.
     
    Determinations of total mold count
     
    No mold was detected in any treatment on days 1, 5 and 10. According to SLS 731 (2008), curd should contain fewer than 10 molds per gram. On day 15, molds were absent in T2–T6, while T1 recorded 7.5±1.29, within the acceptable limit. On day 16, T4-T6 remained mold-free; T2 (6.75±0.50) and T3 (5.5±0.58) were within limits, whereas T1 (867.75±8.06) exceeded the standard. By day 17, T2 (952.25±6.60) and T3 (740.25 ±10.81) surpassed limits, while T4 (8±0.82), T5 (7.25±0.96) and T6 remained safe.

    On days 19 and 20, all treatments exceeded SLS limits. Yeast counts decreased with increasing aloe vera concentration, indicating antimicrobial effects of aloe bioactive compounds (Srikanth, 2017).
     
    Determination of total plate count
     
    The permissible total plate count (TPC) for curd is <10w  (Chaudhary et al., 2011). None of the treatments exceeded this limit during the initial storage stages (Days 1, 5, 10, 15). On Day 16, T1 (1.41×10x ±0.009×10x ) exceeded the limit, while others remained compliant. By Day 17, T2 (2.21×10x ±0.020×10x ) and T3 (1.62×10x  ±0.035×10x ) also surpassed the limit, with T4, T5 and T6 still within acceptable levels. On Day 18, T4 and T5 exceeded the limit, leaving T6 as the only compliant treatment. Beyond Day 18, all treatments surpassed the permissible limit, with T6 showing the longest storage stability (18 days) compared to T1 (15 days). Results demonstrate that higher aloe vera juice concentrations (T6) extended curd shelf life due to aloe vera’s bioactive compounds and antimicrobial properties (Srikanth, 2017; Alam et al., 2022). These findings underline aloe vera’s potential to enhance curd stability and storage duration, benefiting the dairy industry.
     
    Determination of E. coli and coliform count
     
    All aloe vera curd treatments complied with SLS 824:1989, showing no E. coli or coliforms throughout storage, indicating hygienic preparation and aloe vera’s antimicrobial action. Bioactive compounds like acemannan and aloin contributed to microbial safety and extended shelf life (Hamman, 2008; Kambizi and Afolayan, 2001).
     
    Cost-benefit analysis
     
    Table 7 shown the cost of production of various formulated aloe vera curd samples produced from 6L of cow milk. The cost of producing by using 1L of cow milk and 1L of aloe vera juice was LKR 620.00, T2 was LKR628.50, T3 was LKR 637.00, T4 was LKR 645.50, T5 was LKR 654.00 and T6 was 662.50. Aloe vera curd samples could be quickly released to the food market since this sample has higher nutritional value and acceptable cost compared to the regular market price. Commercially available honey-added NLDB curd was Rs150.00 (Sharma, 2010).

    Table 7: Cost benefit analysis.

    CONCLUSION

    This study demonstrated that curd produced by blending cow milk and aloe vera juice, sweetened with kithul treacle, offers a convenient, ready-to-eat product with enhanced physical, chemical and sensory attributes. Kithul treacle, a natural sweetener rich in antioxidants, minerals and proteins, replaced white sugar, while aloe vera juice contributed vitamins, minerals, enzymes, polysaccharides and antioxidants, enhancing nutritional and health benefits. Optimal quality was achieved in T4, which exhibited superior nutritional value, acceptability, a light brown color, firm consistency, smooth texture and pleasant aroma. The production cost of T4 (80 ml) was Rs. 117.00, with potential cost reductions through alternative packaging. T4 also offered an extended shelf life of 18 days, outperforming commercially available honey-added NLDB curd in cost and quality. This innovative product promises to revolutionize the dairy industry by providing an affordable, nutrient-rich curd option that aligns with consumer preferences and market demands.

    CONFLICT OF INTEREST

    The authors declare that there is no conflict of interest regarding the publication of this manuscript.

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